Vehicle windshield

ABSTRACT

The present invention relates to a vehicle windshield including a laminated glass in which a first glass plate, a first adhesive layer, an infrared reflective film, a second adhesive layer, and a second glass plate are laminated in this order, wherein a total thickness of the first glass plate and the second glass plate is 4.1 mm or less, the infrared reflective film contains a laminate in which 100 or more resin layers having different refractive indexes are laminated, the infrared reflective film has thermal contraction rates, wherein a thermal contraction rate in the direction which the thermal contraction rate being maximum is 1.5% or more and 2.0% or less, and a thermal contraction rate in the direction orthogonal to the aforementioned direction is 1.5% or more and 2.0% or less.

CROSS-REFERENCE TO RELATED APPLICATIONS

This U.S. non-provisional application is a continuation application ofand claims the benefit of priority under 35 U.S.C. § 365(c) from PCTInternational Application PCT/JP2019/015916 filed on Apr. 12, 2019,which is designated the U.S., and is based upon and claims the benefitof priority of Japanese Patent Application No. 2018-080601 filed on Apr.19 2018, the entire contents of which are incorporated herein byreference.

TECHNICAL FIELD

The present invention relates to a vehicle windshield, and moreparticularly to a vehicle windshield formed of a laminated glass usingan infrared reflective film.

BACKGROUND OF THE INVENTION

Conventionally, as a laminated glass used for a vehicle windshield, alaminated glass in which an infrared reflective film is sandwichedbetween a pair of glass plates via an adhesive layer is known. Alaminated glass is produced, for example, by stacking a glass plate, anadhesive layer, an infrared reflective film, an adhesive layer, and aglass plate in this order. Then, the entire laminated glass is heatedand pressed to integrate them. In the production of such laminatedglass, unevenness due to pressure because of uneven thickness ofadhesive layers, warp or wrinkles of films due to the difference in thethermal contraction rate between the films and the adhesive layers aregenerated in the film, resulting in impairing the appearance of thelaminated glass. Accordingly, the solution to solve this problem hasbeen considered.

For example, Patent Document 1 discloses the technique of a multilayerlaminated film which defines thermal contraction stress of a film so asto suppress unevenness in an appearance of the film in the multilayerlaminated film having a function of interfering and reflecting infraredrays by alternately laminating resin layers having different refractiveindexes.

Further, Patent Document 2 discloses a laminated glass in which any oneof a thermal contraction rate, an elastic modulus, and an elongation ofthe infrared reflective film is controlled so as to fall within apredetermined range in order to suppress wrinkles of the film, which areparticularly likely generated at the edge of the film in the case ofusing a glass plate curved by bending.

On the other hand, it is known that a phenomenon in which the contour ofa reflected image appears to fluctuate, so-called orange peel, isgenerated in a laminated glass using an infrared reflective film.Generation of orange peel on vehicle windshields is not preferable fromthe viewpoint of appearance and visibility from vehicle interior-side.The cause of orange peel is considered to be the waviness of theinfrared reflective film itself generated during the production oflaminated glass, or the waviness of the film surface due to the infraredreflective film being pulled toward the center due to the contraction ofthe adjacent adhesive layer.

As described above, Patent Document 1 and Patent Document 2 disclosesuppressing of deterioration of the appearance of the laminated glasssuch as unevenness and wrinkles due to the infrared reflective film.However, these conventional techniques do not consider to improve othercharacteristics demanded for windshields for vehicles while suppressingthe generation of orange peel.

RELATED-ART DOCUMENT Patent Documents

Patent document 1: International Patent Publication No. 2013/137288

Patent document 2: Japanese Unexamined Patent Publication No.2010-180089

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

The present invention provides a vehicle windshield containing alaminated glass using an infrared reflective film, which has excellentheat shield properties and a good appearance. In particular, the vehiclewindshield of the present invention is capable of suppressing thegeneration of a phenomenon in which the contour of the reflected imageappears to fluctuate (hereinafter, also referred to as “orange peel”).

Means for Solving the Problems

A vehicle windshield includes a laminated glass in which a first glassplate, a first adhesive layer, an infrared reflective film, a secondadhesive layer, and a second glass plate are laminated in this order,wherein a total thickness of the first glass plate and the second glassplate is 4.1 mm or less, the infrared reflective film contains alaminate in which 100 or more resin layers having different refractiveindexes are laminated, the infrared reflective film has thermalcontraction rates, wherein a thermal contraction rate in the directionwhich the thermal contraction rate being maximum is 1.5% or more and2.0% or less, and a thermal contraction rate in the direction orthogonalto the aforementioned direction is 1.5% or more and 2.0% or less, andthe thermal contraction rates of the infrared reflective film in thepredetermined directions being reduction rates of lengths in thepredetermined directions before versus after maintaining the infraredreflective film at 150° C. for 30 minutes, and a thickness of theinfrared reflective film is 80 μm or more and 120 μm or less.

Effect of the Invention

According to the present invention, the present invention provides avehicle windshield containing a laminated glass using an infraredreflective film, which has excellent heat shield properties and a goodappearance. In particular, the vehicle windshield of the presentinvention is capable of suppressing the generation of a phenomenon inwhich the contour of the reflected image appears to fluctuate(hereinafter, also referred to as “orange peel”).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an example of the front view of the laminated glass whichforms the vehicle windshield in an embodiment of this invention.

FIG. 2 is a cross-sectional view taken along the line X-X of thelaminated glass shown in FIG. 1.

FIG. 3 is a figure explaining the method of evaluating the distortion ofthe transmitted image in Examples.

FIG. 4 is another figure for explaining the method of evaluating thedistortion of the transmitted image in Examples.

FIG. 5 is still another figure for explaining the method of evaluatingthe distortion of the transmitted image in Examples.

DETAILED DESCRIPTION

Embodiments of the present invention will be described below. Thepresent invention is not limited to these embodiments, and theseembodiments can be changed or modified without departing from the spiritand scope of the present invention.

The vehicle windshield of the present embodiment (hereinafter, simplyreferred to as “windshield”) includes a laminated glass in which a firstglass plate, a first adhesive layer, an infrared reflective film, asecond adhesive layer, and a second glass plate are laminated in thisorder, wherein the total thickness of the first glass plate and thesecond glass plate is 4.1 mm or less, and the infrared reflective filmhas the following requirements of (1) to (3).

(1) The infrared reflective film includes a laminate in which 100 ormore resin layers having different refractive indexes are laminated.(2) The infrared reflective film has thermal contraction rates, whereina thermal contraction rate in the direction which the thermalcontraction rate being maximum is 1.5% or more and 2.0% or less, and athermal contraction rate in the direction orthogonal to theaforementioned direction is 1.5% or more and 2.0% or less, and thethermal contraction rates of the infrared reflective film in thepredetermined directions being reduction rates of lengths in thepredetermined directions before versus after maintaining the infraredreflective film at 150° C. for 30 minutes.(3) The thickness of the infrared reflective film is 80 μm or more and120 μm or less.

By satisfying the requirement (1), the infrared reflective film hasinfrared reflectivity due to interference reflection. When the infraredreflective film satisfies the requirements (2) and (3), most of thefactors that deform the infrared reflective film during themanufacturing of the windshield are eliminated. Accordingly, thewindshield of the embodiment that has excellent heat shieldingproperties and that suppresses the generation of orange peel can beobtained. Hereinafter, the windshield of the present embodiment will bedescribed with reference to the drawings.

FIG. 1 is an example of a plan view of a laminated glass forming thewindshield according to the embodiment. FIG. 1 is a plan view of alaminated glass seen from the vehicle interior-side. FIG. 2 is across-sectional view of the laminated glass taken along the line X-X ofFIG. 1.

In the present specification, “upper” and “lower” indicate the upperside and the lower side of the windshield when the windshield is mountedon a vehicle, respectively. The “vertical direction” of the windshieldindicates the vertical direction of the windshield when the windshieldis mounted on a vehicle, and the direction orthogonal to the verticaldirection is called the “width direction of the vehicle”.

In addition, in the present specification, the peripheral edge portionof the glass plate refers to a region having a certain width from theend portion of the glass plate toward the center of the main surface. Inthe present specification, the outer peripheral side portion of the mainsurface of the laminated glass for a vehicle viewed from the center ofthe main surface is referred to as the exterior-side, and the centralside portion of the main surface viewed from the outer periphery of themain surface is referred to as interior-side. In the presentspecification, “substantially the same shape” and “same size” refer to astate when a person considers a shape is the same or a size is the same.In other cases, “substantially” has the same meaning as above. Further,“to” representing the numerical range includes the upper limit value andthe lower limit value.

In FIGS. 1 and 2, a laminated glass 10 used as a windshield(hereinafter, also referred to as “windshield 10”) has a first glassplate 1, a first adhesive layer 3, an infrared reflective film 5, asecond adhesive layer 4, and a second glass plate 2, in which each has amain surface of the same shape and the same size. In the windshield 10of the present embodiment, the first glass plate 1 is arranged on thevehicle interior-side. The windshield 10 further has a black ceramiclayer 6 arranged in a strip shape, in other words, in a frame shape,over the entire peripheral edge portion on the main surface of thevehicle interior-side of the first glass plate 1.

In the windshield of the present invention, the black ceramic layer is,for example, a component that is optionally provided in order to concealthe vehicle body mounting portion of the windshield and suppress thedeterioration of the adhesive in that portion due to ultraviolet rays.In the windshield 10, a region having the black ceramic layer 6 in aplan view is referred to as a light shielding region 10 x that does nottransmit at least visible light, and a region excluding the lightshielding region 10 x is referred to as a transparent area 10 y.

The top of the front view shown in FIG. 1 corresponds to the top of thewindshield. The cross-sectional view of FIG. 2 is a cross-sectional viewin which the left side of the drawing is on the windshield. Hereinafter,each component of the windshield 10 will be described.

[Infrared Reflective Film]

The infrared reflective film 5 on the windshield 10 satisfies the aboverequirements (1) to (3). According to the requirement (1), the infraredreflective film includes a laminate in which 100 or more resin layershaving different refractive indexes are laminated. The infraredreflective film 5 has infrared reflectivity by including the laminate.The infrared reflective film 5 may be formed from only the laminate, andmay optionally have another layer, for example, a protective layerdescribed later, as long as the effects of the invention are notimpaired.

Regarding the requirement (1), in the infrared reflective film 5, thenumber of types of resin layers having different refractive indexesforming the laminate may be 2 or more, preferably 2 or more and 4 orless, and particularly 2, from the viewpoint of ease of production. Whentwo types of resin layers having different refractive indexes are used,a resin layer having a relatively high refractive index is called a highrefractive index layer and a resin layer having a low refractive indexis called a low refractive index layer. In this case, the laminate isusually formed by alternately laminating high refractive index layersand low refractive index layers.

The refractive index of the resin layer is given as the refractive indexof a wavelength of 589 nm measured using sodium D line as a lightsource. The high refractive index layer preferably has a refractiveindex in the range of 1.62 to 1.70, and the low refractive index layerpreferably has a refractive index in the range of 1.50 to 1.58. Further,the difference in refractive index between the high refractive indexlayer and the low refractive index layer is preferably in the range of0.05 to 0.20, more preferably in the range of 0.10 to 0.15.

The refractive index of the resin layer can be adjusted by appropriatelyadjusting the type of resin, the types of functional groups andskeletons in the resin, and the content of the resin. The resinconstituting the resin layer is preferably a thermoplastic resin.Examples of the thermoplastic resin include polyolefin, alicyclicpolyolefin, polyamide, aramid, acrylic resin, polyvinyl chloride,polyvinylidene chloride, polystyrene, styrene copolymer, polycarbonate,polyester, polyether sulfone, polyether ether ketone, modifiedpolyphenylene ether, polyphenylene sulfide, polyetherimide, polyimide,polyarylate, fluorine-containing resin, and the like.

Two or more kinds of resins having different refractive indexes areappropriately selected from the above resins, and resin layers formed ofthe selected resins are laminated according to the above design to forma laminate. When selecting resins having different refractive indices,it is preferable to select a combination of resins containing the samerepeating unit from the viewpoints of interlayer adhesion and thefeasibility of a highly accurate laminated structure. Among the aboveresins, polyester is preferably used from the viewpoint of strength,heat resistance and transparency, and it is preferable to select acombination containing the same repeating unit from polyester. As thepolyester to be selected, a polyester obtained by using an aromaticdicarboxylic acid or an aliphatic dicarboxylic acid and a diol or aderivative thereof is preferably used.

Examples of the polyesters include polyethylene terephthalate,polyethylene terephthalate copolymer, polyethylene naphthalate,polyethylene naphthalate copolymer, polybutylene terephthalate,polybutylene terephthalate copolymer, polybutylene naphthalate,polybutylene naphthalate copolymer, polyhexamethylene terephthalate,polyhexamethylene terephthalate copolymer, polyhexamethylenenaphthalate, polyhexamethylene naphthalate copolymer, and the like. Itis preferable to use one or more polyesters selected from the abovepolyesters.

Among these, the resin constituting the resin layer having a differentrefractive index is preferably a combination containing at least onetype selected from polyethylene terephthalate (hereinafter referred toas “PET”) and polyethylene terephthalate copolymer (hereinafter referredto as “PET copolymer”). When the laminate is configured by alternatelylaminating two types of resin layers, for example, one resin layer isformed of PET, and the other resin layer is formed of PET copolymer, ora resin composed of a mixture of at least two types selected from PETand PET copolymer (hereinafter, also referred to as “mixed PET”).

The PET copolymer is composed of an ethylene terephthalate unit, whichis the same repeating unit as PET, and a repeating unit having anotherester bond (hereinafter, also referred to as “other repeating unit”).The proportion of other repeating units having an ester bond(hereinafter, also referred to as “copolymerization amount”) ispreferably 5 mol % or more in order to obtain different refractiveindexes. In addition, the amount of copolymerization is preferably 90mol % or less because the adhesiveness between the layers is excellent,and further, the accuracy of the thickness of each layer and theuniformity of the thickness are excellent due to the small difference inheat flow characteristics. More preferably, the amount of thecopolymerization is 10 mol % or more and 80 mol % or less.

When the mixed PET is a mixture of PET and a PET copolymer or a mixtureof two or more kinds of PET copolymers, each component is preferablymixed in the mixture so that the content ratio of the other repeatingunits in the mixture become the same amount as that of the PET copolymerof the above.

The absolute value of the difference in glass transition temperaturebetween resin layers having different refractive indexes is preferably20° C. or less. When the absolute value of the difference in glasstransition temperature is larger than 20° C., the uniformity of filmthickness may be poor when the infrared reflective film including thelaminate is formed, and the infrared reflectivity may vary. Further,there is a problem such as overstretching when molding an infraredreflective film including a laminate.

The mixed PET preferably contains, as another repeating unit, arepeating unit derived from spiroglycol as a raw material diol.Hereinafter, the repeating unit derived from the raw material componentwill be described by adding a unit to the raw material compound name.For example, a repeating unit derived from spiroglycol is referred to as“spiroglycol unit”. The mixed PET contains spiroglycol units means thatthe mixed PET contains a PET copolymer having spiroglycol units. Themixed PET may consist only of a PET copolymer having a spiroglycol unit,or may be a mixture of the PET copolymer and PET. In the followingdescription, the mixed PET containing a unit of a specific compoundmeans the same structure as the mixed PET containing a spiroglycol unit.Mixed PET containing a spiroglycol unit is preferable because it has asmall difference in glass transition temperature from PET.

The mixed PET preferably contains, as another repeating unit, acyclohexanedicarboxylic acid unit in addition to the spiroglycol unit.Since the mixed PET containing the spiroglycol unit and thecyclohexanedicarboxylic acid unit has a small glass transitiontemperature difference from PET and a large refractive index differencefrom PET, a laminate having high infrared reflectivity can be obtained.

When the mixed PET contains a spiroglycol unit and acyclohexanedicarboxylic acid unit, the copolymerization amount of thespiroglycol unit is preferably 5 mol % to 30 mol % and thecopolymerization amount of the cyclohexanedicarboxylic acid unit ispreferably 5 mol % to 30 mol %.

The mixed PET also preferably contains a cyclohexanedimethanol unit asanother repeating unit. Mixed PET containing a cyclohexanedimethanolunit is preferably used because the difference of the glass transitiontemperature of the mixed PET and that of PET is small.

When the mixed PET contains a cyclohexanedimethanol unit, the amount ofcopolymerization of the cyclohexanedimethanol unit is preferably 15 mol% or more and 60 mol % or less in order to achieve both infraredreflectivity and interlayer adhesion. Cyclohexanedimethanol has a cis ortrans isomer as a geometrical isomer, and has a chair or boat type as aconformational isomer. Therefore, the mixed PET containing thecyclohexanedimethanol unit is less likely to be oriented andcrystallized even when co-stretched with PET, has high infraredreflectivity, has less change in optical characteristics due to heathistory, and is less likely to cause problems during film formation.

The intrinsic viscosity (IV) of the PET and the mixed PET used in theabove is preferably 0.4 to 0.8, and more preferably 0.6 to 0.75 from theviewpoint of stability of film formation.

The combination of PET and mixed PET has been described above. In thepresent invention, the combination is not limited to the above, anddifferent mixed PET may be combined depending on the requiredcharacteristics. In that case, a combination in which the types of unitsconstituting the mixed PET are the same and the compositions of therepeating units are different is preferably used.

The laminate has a function of interfering and reflecting infrared raysby stacking 100 or more of such resin layers having different refractiveindexes. When the number of laminated layers of the laminate is 100 ormore, the number of laminated layers can be appropriately adjustedwithin a range in which the film thickness of the infrared reflectivefilm 5 satisfies the requirement (3). In order to improve the infraredreflectivity, the number of resin layers is preferably 400 or more andmore preferably 600 or more. The upper limit of the number of laminatedlayers of the laminate is limited by the upper limit of the filmthickness of the infrared reflective film 5, and about 5000 layers arepreferably used.

The number of resin layers laminated and the layer thickness of eachresin layer in the laminate are designed based on the refractive indexof the resin layer used, depending on the required infraredreflectivity. For example, when the A layer and the B layer are used asthe two types of resin layers having different refractive indexes, thelayer thickness distribution is that the optical thicknesses of theadjacent A layer and B layer satisfy the following formula (i).

λ=2(n _(A) d _(A) +n _(B) d _(B))  (i)

Here, A is the wavelength of reflected light, n_(A) is the refractiveindex of the A layer, d_(A) is the thickness of the A layer, n_(B) isthe refractive index of the B layer, and d_(B) is the thickness of the Blayer.

Further, the layer thickness distribution preferably satisfies theformula (i) and the following formula (ii) at the same time.

n _(A) d _(A) =n _(B) d _(B)  (ii)

Even-order reflection can be eliminated by having the layer thicknessdistribution that simultaneously satisfies the formulae (i) and (ii).Thereby, for example, the average reflectance in the wavelength range of400 nm to 700 nm (visible light) can be lowered while increasing theaverage reflectance in the wavelength range of 850 nm to 1200 nm(infrared ray). Accordingly, the infrared reflective film 5 which istransparent and has a high cut off property of heat energy can beobtained.

In addition to the formulae (i) and (ii), the 711711 structure (U.S.Pat. No. 5,360,659) for the layer thickness distribution is alsopreferably applied. The 711711 structure is a laminated structure inwhich 6 layers having A layer and the B layer are laminated in the orderof ABABAB are used as one repeating unit and the ratio of opticalthickness in one unit is 711711. Due to the layer thickness distributionhaving the 711711 structure, higher order reflections can be eliminated.Thereby, for example, the average reflectance in the wavelength range of850 nm to 1400 nm can be increased and the average reflectance in thewavelength range of 400 nm to 700 nm can be decreased. Further, light inthe wavelength range of 850 nm to 1200 nm may be reflected by the layerthickness distribution satisfying the formulae (i) and (ii) at the sametime, and light in the wavelength range of 1200 nm to 1400 nm may bereflected by the layer thickness distribution of the 711111 structure.Light can be efficiently reflected with a small number of layers byapplying the layer thickness structure as above.

Examples of the layer thickness distribution preferably include suchthat the layer thickness distribution increases or decreases from onesurface of a film to the opposite surface thereof, the layer thicknessdistribution increases from one surface of a film to the center of thefilm thickness and then decreases from the center of the film to theopposite surface of the film, and the layer thickness distributiondecreases from one surface of a film to the center of the film thicknessand then increases from the center of the film to the opposite surfaceof the film. As a mode of change of the layer thickness distribution, asequential change such as a linear change, a geometrical change, astepwise change, or a step-like change such that layer thickness changedby almost the same layer thickness of about 10 to 50 layers ispreferably applied.

The infrared reflective film 5 may have a resin layer having a layerthickness of 3 μm or more as a protective layer on both surface layersof the laminate. The thickness of the protective layer is preferably 5μm or more, and more preferably 10 μm or more. When the thickness of theprotective layer is increased, the effect of suppressing the flow markand suppressing the ripple of the transmittance/reflectance spectrum canbe obtained. However, the protective layer is provided in the rangewhere the infrared reflective film 5 satisfies the requirements (1) and(3).

According to the requirement (3), the thickness of the infraredreflective film 5 is 80 μm or more and 120 μm or less. The infraredreflective film 5 has rigidity by having a thickness of 80 μm or more,and is hardly affected by thermal contraction of the first adhesivelayer and the second adhesive layer during the production of laminatedglass. Accordingly, the generation of orange peel can be suppressed.When the thickness of the infrared reflective film 5 is 120 μm or less,the degassing property during the production of laminated glass isfavorable. The thickness of the infrared reflective film 5 is preferably85 μm or more and 115 μm or less, more preferably 90 μm or more and 110μm or less, and further preferably 95 μm or more and 110 μm or less.

According to the requirement (2), the infrared reflective film 5 has athermal contraction rate in a direction which the thermal contractionrate being maximum (hereinafter also called “direction for maximumcontraction”) of 1.5% or more and 2.0% or less, and has a thermalcontraction rate in a direction orthogonal to the direction hereinafteralso called “orthogonal direction”) of 1.5% or more and 2.0% or less.

However, the thermal contraction rates of the infrared reflective filmin the predetermined directions being reduction rates of lengths in thepredetermined directions before versus after maintaining the infraredreflective film at 150° C. for 30 minutes. Specifically, the thermalcontraction rate of the infrared reflective film can be measured asfollows.

First, a strip-shaped test piece is cut out from the infrared reflectivefilm 5 along the direction for maximum contraction or the orthogonaldirection thereto. The infrared reflective film has residual stress dueto stretching, because the infrared reflective film is manufactured bystretching the constituent materials into a film as described below. Inparticular, the residual stress in the longitudinal direction which isthe flow direction at the time of film production, that is, theso-called MD direction, is large and thermal contraction is likelygenerated. Therefore, normally, the MD direction is the direction formaximum contraction and the TD direction which is the width direction isthe orthogonal direction.

The dimensions of the test piece are, for example, 150 mm in length and20 mm in width. On this test piece, a pair of reference lines arewritten at intervals of about 100 mm in the longitudinal direction, andthe length L₁ between the reference lines is measured. The test piece ishung vertically in a hot air circulation oven, heated to 150° C. andmaintained for 30 minutes. The test piece is naturally cooled to roomtemperature and maintained for 60 minutes, and then the length L₂between the reference lines is measured. The thermal contraction rate iscalculated by the following formula (iii) by substituting the L₁ and L₂obtained above.

Thermal contraction rate=((L ₁ −L ₂)/L ₁)×100[%]  (iii)

The generation of orange peel in the infrared reflective film 5 can besuppressed when the thermal contraction rate in the direction formaximum contraction of the film and the orthogonal direction of the filmis 1.5% or more, and the generation of transparent warp of the laminatedglass can be suppressed when the thermal contraction rate is 2.0% orless. The thermal contraction rate in a direction in which the thermalcontraction rate being maximum is preferably 1.6% or more and 2.0% orless and more preferably 1.8% or more and 2.0% or less. The thermalcontraction rate in a direction orthogonal to the direction ispreferably 1.6% or more and 2.0% or less and more preferably 1.75% ormore and 2.0% or less. Further, a small difference between the thermalcontraction rate in the direction for maximum contraction and thethermal contraction rate in the orthogonal direction is favorable. Thethermal contraction rate in the direction for maximum contraction andthe thermal contraction rate in the orthogonal direction being the sameis particularly favorable.

The infrared reflective film 5 satisfying the requirements (1) to (3)can be produced, for example, by the following method. In addition,below, the method of producing the infrared reflective film 5 whichconsists of a laminate using the A layer formed of resin A and the Blayer formed of resin B is exemplified as two types of resin layershaving different refractive indexes. An infrared reflective film usingthree or more kinds of resin layers or an infrared reflective filmhaving another layer such as a protective layer can be produced byappropriately changing the method.

The infrared reflective film formed by a laminate using the A layer andthe B layer can be produced by a method including the following steps(a) to (c). When the infrared reflective film satisfying all the aboverequirements (1) to (3) is obtained in the steps (a) and (b), the step(c) is not performed. That is, the step (c) can be an optional step.

(a) A step of producing an unstretched laminate in which A layers and Blayers are alternately laminated so that the layer thickness isdifferent from that of the finally obtained laminate but the number oflayers is the same.(b) A step of stretching the unstretched laminate obtained in the step(a) to adjust the layer thickness to obtain a laminate precursor.(c) A step of heat-treating the laminate precursor after the step toobtain a laminate having a thermal contraction adjusted to satisfy therequirement (2).

(a) Step of Producing Unstretched Laminate

Resin A and resin B are prepared in the form of pellets or the like. Thepellets are pre-dried in hot air or under vacuum, as needed, and thensupplied to the extruder. In the extruder, the resin that has beenheated and melted at a temperature equal to or higher than the meltingpoint has a uniform amount of resin extruded by a gear pump or the like,and foreign matter and modified resin are removed through a filter orthe like.

The resin A and the resin B sent out from different flow paths by usingtwo or more extruders are then transferred to a multi-layer laminatingapparatus to be a molten laminate in which a desired number of layers islaminated by the apparatus. Then, the molten laminate is formed into adesired shape with a die and discharged. The multilayered sheetsdischarged from the die are extruded onto a cooling body such as acasting drum, and the sheets are cooled and solidified to form anunstretched laminate. A multi-manifold die, a field block, a staticmixer, or the like can be used as the multi-layer laminating apparatus.

(b) Step of Stretching

The unstretched laminate obtained in the step (a) is stretched toprepare a laminate precursor. The stretching method is usually biaxialstretching. The biaxial stretching method may be either sequentialbiaxial stretching or simultaneous biaxial stretching. Furthermore,re-stretching may be performed in the MD direction and/or the TDdirection. Simultaneous biaxial stretching is preferred from theviewpoint of suppressing in-plane orientation difference and suppressingsurface scratches. The biaxial stretching is preferably carried out at atemperature not lower than the glass transition temperature of the resinhaving the higher glass transition point of the resin A and the resin Bbut not higher than the temperature+120° C.

The stretching ratios in the MD direction and the TD direction areadjusted so that the layer thickness of each layer in the obtainedlaminate is the designed layer thickness. Further, preferably, thestretching ratio and the stretching speed are adjusted so that theresidual stress in the MD direction and the TD direction are almost thesame. The laminate precursor obtained in the stretching step usually hashigh residual stress and does not satisfy the requirement (2) in theinfrared reflective film. Then, the following heat treatment (c) isperformed to obtain a laminate satisfying the requirement (2). However,as described above, when the laminate precursor satisfies therequirement (2), the laminate precursor may be used as it is as alaminate.

(C) Step of Heat Treatment

The heat treatment of the laminate precursor is generally performed in astretching machine. The heat treatment temperature is preferably lowerthan the melting point of the resin having a higher melting pointbetween the resins A and B. Also, the heat treatment temperature ispreferably higher than the melting point of the resin having a lowermelting point between the resins A and B. As a result, the resin havingthe higher melting point maintains the high orientation state, while theorientation of the resin having the lower melting point is relaxed, sothat the difference in refractive index between these resins can beeasily provided. Further, the stress of the thermal contraction iseasily reduced as the orientation is relaxed. Thereby, the thermalcontraction rate of the laminate can be easily adjusted within the rangeof (2).

Note that the heat treatment may be performed so that the relaxationrate at the time of heat treatment is 0% or more and 10% or less andpreferably 0% or more and 5% or less. The relaxation may be performed inone or both of the TD direction and the MD direction. It is alsopreferable to perform a fine stretching of 2% or more and 10% or lessduring the heat treatment. The fine stretching may be performed in oneor both of the TD direction and the MD direction. In this way, the heattreatment temperature, the heat treatment time, the relaxation rate andthe fine stretching rate are adjusted so that the thermal contractionrate of the laminate falls within the range of (2).

In addition, for the purpose of adjusting the thermal contraction rateof the laminate, a thermal relaxation may be performed during coolingafter the heat treatment step, and further, fine stretching may beperformed after the heat treatment step.

In the windshield 10, the infrared reflective film 5 is placed so thatthe direction for maximum contraction of the film substantiallycoincides with the vertical direction of the windshield 10 or thevehicle width direction. In this case, substantially coincides isdefined such that the angle deviation of each component forming theinfrared reflective film is within ±5°.

[Adhesive Layer]

The first adhesive layer 3 and the second adhesive layer 4 in thewindshield 10 have main surfaces of the same shape and the same size asthe main surfaces of the first glass plate 1 and the second glass plate2, and the formation of the thicknesses of the adhesive layers are flatlayers as described later. The first adhesive layer 3 and the secondadhesive layer 4 are inserted between the first glass plate 1 and thesecond glass plate 2 while sandwiching the infrared reflective film 5therebetween. The adhesive layer has a function to adhere these and hasa function to integrate to form the windshield 10 as a whole.

The first adhesive layer 3 and the second adhesive layer 4 can be thesame configuration except the position placed on the windshield 10.Hereinafter, the first adhesive layer 3 and the second adhesive layer 4will be collectively described as “adhesive layer”.

The adhesive layer is formed of an adhesive layer containing athermoplastic resin used for an ordinary laminated glass adhesive layer.The kind of the thermoplastic resin is not particularly limited, and canbe appropriately selected from the known thermoplastic resins formingthe adhesive layer.

Examples of the thermoplastic resin include polyvinyl acetal such aspolyvinyl butyral (PVB), polyvinyl chloride (PVC), saturated polyester,polyurethane, ethylene-vinyl acetate copolymer (EVA), ethylene-ethylacrylate copolymer, cycloolefin polymer (COP), and the like. Thethermoplastic resins may be used alone or in combination of two or morekinds.

The thermoplastic resin is selected in consideration of the balance ofvarious properties such as glass transition point, transparency, weatherresistance, adhesive strength, penetration resistance, impact energyabsorption, moisture resistance, and heat shielding property. The glasstransition point of the thermoplastic resin can be adjusted, forexample, by the amount of a plasticizer. Considering the balance of theabove performances, the thermoplastic resin used for the adhesive layeris preferably PVB, EVA, polyurethane or the like. Furthermore, PVB isparticularly preferable in consideration of reducing the amount ofdeformation of the infrared reflective film 5 when the windshield 10 isproduced.

The adhesive layer contains a thermoplastic resin as a main component.The adhesive layer contains a thermoplastic resin as a main component,indicates that the content of the thermoplastic resin with respect tothe total amount of the adhesive layer is 30% by mass or more. Theadhesive layer may contain one kind or two or more kinds of variousadditives such as an infrared absorber, an ultraviolet absorber, afluorescent agent, an adhesion modifier, a coupling agent, a surfactant,an antioxidant, a heat stabilizer, a light stabilizer, a dehydratingagent, a defoaming agent, an antistatic agent, a flame retardant, andthe like.

In the adhesive layer, a thermal contraction rate in a direction inwhich a thermal contraction rate being maximum (hereinafter, alsoreferred to as “direction for maximum contraction” similarly to theinfrared reflecting film) is preferably 2.0% or more and 8.0% or less,and the thermal contraction rate in a direction orthogonal to thedirection (hereinafter, also referred to as “orthogonal direction”similarly to the infrared reflecting film) is preferably 2.0% or moreand 8.0% or less. The thermal contraction rate in a direction in which athermal contraction rate being maximum in the adhesive layer ispreferably 4.0% or more and 7.0% or less, and the thermal contractionrate in the direction orthogonal to the direction is preferably 4.0% ormore and 7.0% or less.

The thermal contraction rate of the adhesive layer is a reduction ratioof length in the specified direction of the adhesive layer before andafter heat treatment. When the time point at leaving the adhesive layerfor 24 hours or more in the constant temperature and humidityenvironment of the temperature of 20° C. and the humidity of 55% isregarded as before heat treatment. Then, when the time point cooling theadhesive layer in a desiccator at 20° C. for 1 hour after keeping theadhesive layer at 50° C. for 10 minutes is regarded as after heattreatment. The thermal contraction rate of the adhesive layer issimilarly measured as the thermal contraction rate of the infraredreflective film except that the heat treatment temperature and the testtime are changed to at 50° C. for 10 minutes, and pretreatment andposttreatment are performed before and after the heat treatment.

In the same manner as the infrared reflective film 5, the adhesive layeris produced by stretching the constituent materials into a film. Sincethe residual stress is large in the MD direction, which is the flowdirection at the time of producing the adhesive layer, the adhesivelayer is likely to be heat-shrunken. Therefore, normally, the MDdirection is the direction for maximum contraction and the TD directionwhich is the width direction is the orthogonal direction. When thewindshield 10 is produced by laminating the infrared reflective film 5so that the direction for maximum contraction of the infrared reflectivefilm 5 coincides with the direction for maximum contraction of theadhesive layer, the infrared reflective film 5 is likely to be deformed.

Therefore, in the windshield 10, the adhesive layer is preferably placedso that the direction for maximum contraction of the infrared reflectivefilm 5 and the direction for maximum contraction of the adhesive layerare orthogonal to each other. The direction for maximum contraction ofthe adhesive layer and that of the infrared reflective film arepreferably completely orthogonal to each other, but if the angledeviation from the completely orthogonal state is within ±5° for eachadhesive layer, it is allowable.

Further, in the windshield 10, the value (H) in which the thermalcontraction rate in the direction in which the thermal contraction rateof the infrared reflective film 5 being maximum divided by the averagevalue of the thermal contraction rate in the direction in which thethermal contraction rate of the first adhesive layer 3 and the secondadhesive layer 4 being maximum is 0.2 or more and 0.6 or less. When thenumerical value H is 0.2 or more, the deformation load of the infraredreflective film due to the contraction of the adhesive layer becomessmall, and the appearance defect such as orange peel or wrinkle hardlyoccurs. When the numerical value H is 0.6 or less, the thermalcontraction rate of the adhesive layer and the infrared reflective filmdo not come too close to each other, the contraction of the infraredreflective film does not accelerate, and an appearance defect does notlikely occur due to the infrared reflective film being pulled inward.

The film thicknesses of the first adhesive layer 3 and the secondadhesive layer 4 are not particularly limited. Specifically, thethicknesses of the adhesive layers are preferably 0.3 to 0.8 mm in thesame manner as an adhesive layer usually used for laminated glass forvehicles. The total thickness of the first adhesive layer 3 and thesecond adhesive layer 4 is preferably 0.7 to 1.5 mm. When the thicknessof each adhesive layer is less than 0.3 mm or the total thickness of thetwo layers is less than 0.7 mm, the strength may be insufficient evenwhen the two layers are combined. Conversely, when the thickness of eachadhesive layer exceeds 0.8 mm or the total thickness of the two layersexceeds 1.5 mm, in some cases, a so-called plate misalignment phenomenonmay occur between the first glass plate 1 and the second glass plate 2in which these are sandwiched in the main bonding (main pressurebonding) step by the autoclave at the time of producing the windshield10, which will be described later.

The adhesive layer is not limited to a single layer structure. Forexample, Japanese Patent Application Laid-Open No. 2000-272936 disclosesa multilayer resin film, which is used for the purpose of improvingsound insulation performance and has different properties (differentloss tangents), that may be used as an adhesive layer. Further, in thewindshield 10, the adhesive layer may be designed so that the verticalcross-sectional shape is wedge-shaped. As the wedge shape, the thicknessof the adhesive layer may monotonically decrease from the upper side tothe lower side, or the rate of change of the thickness may be partiallydifferent as long as the thickness of the upper side is larger than thethickness of the lower side. Alternatively, the design may have a parthaving a uniform thickness.

[Glass Plate]

Although the thicknesses of the first glass plate 1 and the second glassplate 2 in the windshield 10 differ depending on the composition thereofand the compositions of the first adhesive layer 3 and the secondadhesive layer 4, thicknesses of glass plates in windshields aregenerally 0.1 to 10 mm.

Of the first glass plate 1 and the second glass plate 2, the thicknessof the first glass plate 1 on the vehicle interior-side is preferably0.5 to 2.0 mm and more preferably 0.7 to 1.8 mm. The thickness of thesecond glass plate 2 on the vehicle exterior-side is preferably 1.6 mmor more because the impact resistance by a flying stone is favorable.The difference in thickness between the two is preferably 0.3 to 1.5 mmand more preferably 0.5 to 1.3 mm, and the second glass plate 2 ispreferably thicker than the first glass plate 1. The thickness of thesecond glass plate 2 on the vehicle exterior-side is preferably 1.6 to2.5 mm and more preferably 1.7 to 2.1 mm.

From the viewpoint of weight reduction, the total thickness of the firstglass plate 1 and the second glass plate 2 is preferably 4.1 mm or less.The total thickness is more preferably 3.8 mm or less, furtherpreferably 3.6 mm or less.

The first glass plate 1 and the second glass plate 2 can be formed ofinorganic glass or organic glass (resin). Examples of the inorganicglass include ordinary soda lime glass (also referred to as soda limesilicate glass), aluminosilicate glass, borosilicate glass, non-alkaliglass, quartz glass and the like. Of these, soda lime glass isparticularly preferable. Examples of the inorganic glass include floatplate glass formed by the float method or the like. As the inorganicglass, glass that has been subjected to tempering treatment such asair-cooled tempering or chemical tempering can also be used.

Examples of the organic glass (resin) include polycarbonate resin,polystyrene resin, aromatic polyester resin, acrylic resin, polyesterresin, polyarylate resin, polycondensate of halogenated bisphenol A andethylene glycol, acrylic urethane resin, acrylic resins containinghalogenated aryl group, and the like. Of these, polycarbonate resinssuch as aromatic polycarbonate resins and acrylic resins such aspolymethylmethacrylate acrylic resins are preferably used, andpolycarbonate resins are more preferably used. Further, among thepolycarbonate resins, the bisphenol A-based polycarbonate resin isparticularly preferably used. Two or more kinds of the above resins maybe used in combination.

The glass may contain an infrared absorber, an ultraviolet absorber orthe like. Examples of such glass include green glass, ultravioletabsorbing (UV) green glass, and the like. The UV green glass containsSiO₂ of 68% by mass or more and 74% by mass or less, Fe₂O₃ of 0.3% bymass or more and 1.0% by mass or less, and FeO of 0.05% by mass or moreand 0.5% by mass or less. In the UV glass, the ultraviolet transmittanceat a wavelength of 350 nm has a minimum value of the transmittance of1.5% or less in the region of 550 nm or more and 1700 nm or less.

The glass may be transparent and may be colorless or colored. Further,the glass may be a laminate of two or more layers. Inorganic glass ispreferably used depending on a place where an inorganic glass applies.

The materials of the first glass plate 1 and the second glass plate 2may be the same or different, but are preferably the same. The shapes ofthe first glass plate 1 and the second glass plate 2 may be flat plates,or may have a curvature on the entire surface or a part thereof. Thesurfaces of the first glass plate 1 and the second glass plate 2 thatare exposed to the atmosphere may be coated with a water-repellentfunction, a hydrophilic function, an antifogging function, or the like.Further, the opposing surfaces of the first glass plate 1 and the secondglass plate 2 may be usually coated with a low radiation coating, aninfrared ray shielding coating, a conductive coating, and the like, butusually coated with a metal layer.

[Black Ceramic Layer]

The black ceramic layer is optionally provided in the windshield of thepresent invention. In the windshield 10, the black ceramic layer 6 isplaced in a frame shape on the main surface of the vehicle interior-sideof the first glass plate 1. When the windshield 10 has the black ceramiclayer 6, the black ceramic layer 6 does not necessarily have to beformed in a strip shape on all four sides of the peripheral edgeportion, and may be formed in a strip shape on a part of the peripheraledge portion.

The width of the black ceramic layer 6 is a width capable of concealinga region that requires concealment. In the windshield 10, the width ofthe black ceramic layer 6 is set to be wider on the lower side than onthe other three sides in order to hide the storage portion such as thewiper. In addition, in the upper side, for example, the central part isdesigned to be wide so that a mounting part such as a communicationdevice, an information acquisition device, or a room-view mirror, andthe like are concealed, and the other parts are designed to be narrow.

Specifically, the width of the black ceramic layer 6 is preferably inthe range of 50 to 300 mm, and more preferably 100 to 200 mm, as thewidth of the lower side and the width of the widely designed portion ofthe upper side. Further, the width of the black ceramic layer 6 providedalong the portion where the width of the upper side is designed to benarrow and along the left and right sides is preferably in the range of5 to 50 mm and more preferably 10 to 30 mm. The widths of the top, theleft, and the right may be the same or different.

Here, the “black” of the black ceramic layer does not mean, for example,black defined by the three attributes of color. The color includescolors recognized as black which is adjusted so that visible light isnot transmitted at least to the extent that the portion where hiding isrequired can be hidden. Therefore, in the black ceramic layer, the blackcolor may have shades within the range where the shielding function canbe performed, and the tint may be slightly different from black definedby the three attributes of color. From the same viewpoint, the blackceramic layer may be configured so that the entire layer becomes acontinuous integral film depending on the location where it is disposed,and the visible light transmission ratio can be easily adjusted bysetting the shape and arrangement. The configuration may be achieved bya dot pattern or the like.

As the black ceramic layer 6, a black ceramic layer formed on the firstglass plate 1 by a conventionally known method can be applied withoutparticular limitation. Specifically, a black ceramic paste obtained byadding a powder of a heat-resistant black pigment to a resin and asolvent together with a low-melting glass powder and kneading is appliedto a desired region of the first glass plate 1 on the vehicleinterior-side by printing or the like. Then, a black ceramic layer isformed by heating and baking. Further, the black pigment used forforming the black ceramic layer includes a combination of pigments thatbecome black by combining a plurality of colored pigments.

The thickness of the black ceramic layer 6 is not particularly limitedas long as a visibility can be obtained without problems. The blackceramic layer 6 is preferably formed with a thickness of about 8 to 20μm and more preferably 10 to 15 μm.

Note that, according to need, the black ceramic layer 6 may be providedon the main surface of the vehicle exterior-side of the first glassplate 1, the main surface of the vehicle interior-side of the secondglass plate 2, or the main surface of the vehicle exterior-side of thesecond glass plate 2.

[Laminated Glass]

The laminated glass constituting the windshield of the present inventionpreferably has a visible light reflectance measured from the vehicleexterior-side of 7% or more and 10% or less. In this specification, whenthe laminated glass 10 has the black ceramic layer 6 as illustrated inFIG. 1, the optical characteristics of the laminated glass, is thecharacteristics of the transparent region 10 which does not have theblack ceramic layer 6 in a plan view.

In the laminated glass 10, when the visible light reflectance (Rv)measured from the vehicle exterior-side is 7% or more, the function ofthe infrared reflective film 5 is sufficient, that is, the heatshielding property is sufficient. When the visible light reflectance(Rv) is 10% or less, orange peel is not noticeable. The visible lightreflectance (Rv) is more preferably 7.5% or more and 10.0% or less.

The laminated glass 10 preferably has a solar radiation transmittance(Te) of 45% or less and a visible light transmittance (Tv) of 70% ormore. The solar radiation transmittance (Te) is more preferably 40% orless and particularly preferably 38% or less. The solar radiationreflectance (Re) measured from the vehicle exterior-side is morepreferably 18% or more and particularly preferably 20% or more. Thevisible light transmittance (Tv) is more preferably 72% or more andparticularly preferably 73% or more. The haze value of the laminatedglass 10 is preferably 1.0% or less, more preferably 0.8% or less, andparticularly preferably 0.6% or less.

The visible light reflectance (Rv) measured from the vehicleexterior-side, the solar radiation reflectance (Re) measured from thevehicle exterior-side, the solar radiation transmittance (Te), and thevisible light transmittance (Tv) are measured by a spectrophotometer bymeasuring the transmittance and the reflectance of the wavelength of 300to 2100 nm. The values of transmittance and reflectance are calculatedby the formula defined in JIS R3106 (1998) and JIS R3212 (1998),respectively. In the present specification, unless otherwise specified,visible light reflectance, solar reflectance, solar radiationtransmittance, and visible light transmittance are the visible lightreflectance measured from the vehicle exterior-side (Rv), the solarradiation reflectance (Re), the solar radiation transmittance (Te) andthe visible light transmittance (Tv). These are the ones measured andcalculated of the above method.

Furthermore, the color tone of the reflected light obtained byirradiating the laminated glass 10 with the light from the D65 lightsource from the vehicle exterior-side in the incident angle range of 10to 60° is preferably −5<a*<3 and −12<b*<2 in CIE1976L*a*b* chromaticitycoordinates. When the values of a* and b* measured under the aboveconditions are out of the above ranges, orange peel become remarkable.The a* measured under the above conditions is more preferably −3<a*<2.The b* measured under the above conditions is more preferably −9<b*<0.

Further, in a test area A (hereinafter, simply referred to as “test areaA”) defined by JIS R3212 (1998) for windshields for vehicles, the radiusof curvature of the laminated glass is preferably 900 mm or less. Theorange peel is not remarkable because the radius of curvature is 900 mmor less. The radius of curvature is more preferably 880 mm or less,further preferably 860 mm or less, and further more preferably 850 mm orless. It is not clear why the orange peel is less noticeable when theradius of curvature is less than or equal to the above upper limit, butit is derived as a result of the inventors' investigation. The fact thatthe radius of curvature of the laminated glass is 900 mm or less in thetest area A indicates that there is no portion in the test area A of thelaminated glass having a radius of curvature of more than 900 mm. Thatis, the maximum radius of curvature in the test area A is 900 mm orless.

In the test area A, the radius of curvature of the laminated glass ispreferably 700 mm or more. When the radius of curvature is 700 mm ormore, defects such as wrinkles are less likely to occur in the infraredreflective film. The radius of curvature is more preferably 750 mm ormore. The fact that the radius of curvature of the laminated glass inthe test region A is 700 mm or more indicates that there is no portionin the test region A of the laminated glass having a radius of curvatureof less than 700 mm. That is, the minimum radius of curvature in thetest area A is 700 mm or more.

The test area A is, in detail, a test area defined as “A test area of asafety glass used for the front” defined in JIS R3212 (1998, “Testmethod for safety glass for automobiles”). FIG. 1 schematically showsthe test area A in the case of the right steering wheel.

The distance between the inner peripheral edge of the black ceramiclayer 6 and the outer peripheral edge of the infrared reflective film 5is preferably 5 mm or more, more preferably 7 mm or more, andfurthermore preferably 10 mm in the portion where the black ceramiclayer 6 and the infrared reflective film 5 overlap in a plan view. Whenthe distance is in the above range, transparent warp can be suppressed.

[Production of Windshields]

The windshield of the present invention can be produced by a commonlyused known technique. In the windshield (laminated glass) 10, the firstglass plate, the first adhesive layer, the infrared reflective film, thesecond adhesive layer, and the second glass plate, in which these areprepared as described above, are laminated in this order by pressurebonding so that a laminated glass precursor is prepared. At that time,according to need, the TD direction and the MD direction of the firstadhesive layer, the infrared reflective film, and the second adhesivelayer are aligned and laminated in preferable directions. The laminatedglass precursor is placed in a vacuum bag such as a rubber bag. Thevacuum bag is connected to an exhaust system, and heated to about 70 to110° C. while applying vacuum suction (degassing) so that the pressureinside the vacuum bag is to be about −65 to −100 kPa (absolute pressureis about 36 to 1 kPa). Thereby, a laminated glass in which the firstglass plate, the first adhesive layer, the infrared reflective film, thesecond adhesive layer, and the second glass plate are entirely bonded isobtained. Thereafter, if necessary, the laminated glass is put into anautoclave, and a pressure bonding process is performed by heating andpressing under conditions of a temperature of about 120 to 150° C. and apressure of about 0.98 to 1.47 MPa. The pressure bonding process canfurther improve the durability of the laminated glass.

EXAMPLES

Hereinafter, the present invention will be described in more detail withreference to Examples. The present invention is not limited to theembodiments described below.

Examples 1 to 11

A laminated glass having the same configuration as the laminated glassillustrated in FIGS. 1 and 2 was produced and evaluated as follows.Examples 1 to 7 are Examples, and Examples 8 to 11 are ComparativeExamples.

(Production of Infrared Reflective Film)

Resin A and resin B were used as two types of thermoplastic resinshaving different refractive indexes. As the resin A, PET (crystallinepolyester, melting point 255° C.) having an intrinsic viscosity IV=0.65and a refractive index 1.66 was used. As the resin B, a PET copolymer(PE/SPG⋅T/CHDC) having an intrinsic viscosity IV=0.73 and a refractiveindex of 1.55 and containing 25 mol % of spiroglycol units, and 30 mol %of cyclohexanedicarboxylic acid units based on all the units was used.The two kinds of prepared resins were melted at 280° C. by an extruder,and 2000 layers were alternately laminated in the thickness direction sothat the optical thickness ratio is to be resin A/resin B=1 to obtain anunstretched laminate.

In each example, the unstretched laminate was biaxially stretched at apredetermined ratio to adjust the thickness of the laminate, and thensubjected to heat treatment to adjust the residual stress (thermalcontraction rate) in the MD direction and the TD direction. An infraredreflective film having the physical properties shown in Table 1 wasobtained. Regarding the thermal contraction rate shown in Table 1, the“direction for maximum thermal contraction” corresponds to the directionin which the thermal contraction rate is maximum, and is specificallythe MD direction of the infrared reflective film. The “orthogonaldirection” shown in Table 1 is a direction orthogonal to the “directionfor maximum thermal contraction” and is the TD direction of the infraredreflective film. The thermal contraction rate of the infrared reflectivefilm is a reduction rate of the length in a predetermined directionbefore and after holding the infrared reflective film at 150° C. for 30minutes, and is a value measured by the above method.

(Production of Laminated Glass)

A heat ray absorbing green glass (manufactured by Asahi Glass Co., Ltd.:NHI (common name)) having a length of 1000 mm, a width of 1400 mm, and aplate thickness of 2 mm was used as the first glass plate. A clear glass(manufactured by Asahi Glass Co., Ltd.: FL (common name)) in which theouter peripheral size in a front view was 1000 mm in length, 1400 mm inwidth, and a plate thickness of 2 mm was used as the second glass plate.Two kinds of glass plates A and B having different radii of curvature inthe test area A were prepared by bending the respective glasses byheating so as to have a predetermined curvature. The maximum radius ofcurvature of the glass plate A in the test area A was 860 mm, and thatof the glass plate B was 1050 mm.

Here, the same radius of curvature and the same kind of glass were usedin the first glass plate and the second glass plate in the production oflaminated glass. In Example 5, the glass plate B was used, and in otherexamples, the glass plate A was used. Further, a black ceramic layer wasformed in a frame shape on the peripheral edge portion of the mainsurface on the vehicle interior-side of the glass plate that became thefirst glass plate.

The first adhesive layer was a PVB film having a thickness of 0.76 mm(Eastman Chemical Company: product number QL51), and the second adhesivelayer was a PVB film having a thickness of 0.38 mm (Eastman ChemicalCompany: product number RK11). In the two types of PVB films havingdifferent thicknesses, the direction in which the thermal contractionrate becomes maximum, specifically, the thermal contraction rate in theMD direction was 6.0%, and the direction orthogonal to the direction formaximum thermal contraction, specifically, the thermal contraction ratein the TD direction was 5.0% in all cases. In addition, the thermalcontraction rate of the PVB film was a value obtained by measuring thePVB film by the above method. Furthermore, two kinds of adhesive layershaving different thermal contraction rates from the above were preparedby adjusting the stretching method. In each case, the first adhesivelayer was a PVB film having a thickness of 0.76 mm, and the secondadhesive layer was a PVB film having a thickness of 0.38 mm. One of theadhesive layers had a thermal contraction rate in the MD direction of8.5% and a thermal contraction rate in the TD direction of 7.0%. Theother adhesive layer had a thermal contraction rate in the MD directionof 3.0% and a thermal contraction rate in the TD direction of 2.0%.

A laminate in which a first glass plate, a first adhesive layer, aninfrared reflective film, a second adhesive layer, and a second glassplate were laminated in this order with use of the infrared reflectivefilm obtained above was prepared in each example. The first adhesivelayer, the infrared reflective film, and the second adhesive layer werelaminated such that the MD direction was aligned with the lateraldirection of the first glass plate and the second glass plate. Inaddition, the first glass plate was laminated such that the blackceramic layer was on the opposite side of the first adhesive layer. Thelaminate was placed in a vacuum bag, and the bag was degassed so thatthe pressure gauge display showed 100 kPa or less. Then, the bag washeated to 120° C. so that the laminate in the bag was subjected topressure bonding. Further, the laminate in the bag was heated at 135° C.and pressurized at 1.3 MPa for 60 minutes in an autoclave. Finally, alaminated glass was obtained by cooling the laminate.

In the laminated glass obtained in each example, visible lightreflectance (Rv) and solar reflectance (Re) were measured. Also, the a*and b* in the CIE1976L*a*b* in the chromaticity coordinates of thereflected light obtained by irradiating the light from the D65 lightsource from the vehicle exterior-side at an incident angle of 100 weremeasured. A spectrophotometer (U4100 manufactured by Hitachi HighTechnology) was used for the measurement. Table 1 shows the obtainedresults, along with the radius of curvature of the glass plate used inexamples.

[Evaluation]

In the obtained laminated glass, an orange peel, a wrinkle, a foaming, atransparent warp, a heat shielding property, and a state of a film beingpulled inward were evaluated.

<Orange Peel>

The laminated glass was horizontally placed in the state in which thebackground of the glass was dark. A straight tube fluorescent light (630mm in length, 30 W, FL30SW manufactured by Mitsubishi Electric LightingCo., Ltd.) was placed 180 cm above from the laminated glass so that thelongitudinal direction of the fluorescent light and the width directionof the laminated glass were in the same direction. Then, the fluorescentlight was turned on. The position of the fluorescent light was adjustedto be directly above the center of the transparent area 10 y of thelaminated glass, and the presence or absence of fluctuation in thecontour of the fluorescent light reflection image in the center wasvisually observed. Similarly, the position of the fluorescent light wasadjusted so as to be directly above the lower side of the transparentarea 10 y of the laminated glass, and the presence or absence offluctuation in the contour of the fluorescent light reflection imagenear the lower side was visually observed. The observation results wereevaluated according to the following criteria.

A: No fluctuation was observed in the contour of the fluorescent lightreflection image.B: Fluctuation was recognized in a part of the contour of thefluorescent light reflection image in the central portion or near thelower side.C: Fluctuations were observed in about half of the contour of thefluorescent light reflection image in the central portion and near thelower side (remarkable defects).

<Wrinkles>

Regarding the transparent area 10 y of the laminated glass, the presenceor absence of wrinkles in the infrared reflective film was visuallyobserved at the peripheral edge portion along the entire outercircumference, and evaluated according to the following criteria.

A: No wrinkles were found on the infrared reflective film at the entireperipheral edge portion of the transparent area 10 y of the laminatedglass.B: A slight wrinkle was observed at a part of the peripheral edgeportion of the transparent area 10 y of the laminated glass.C: Wrinkles were observed at a part of the peripheral edge portion ofthe transparent area 10 y of the laminated glass.

<Foaming>

Regarding the transparent area 10 y of the laminated glass, the presenceor absence of whitening due to air entrainment at the peripheral edgeportion along the entire outer circumference was visually observed andevaluated according to the following criteria.

A: Whitening was not observed at the entire peripheral edge portion ofthe transparent area 10 y of the laminated glass.C: Whitening was observed at a part of the peripheral edge portion ofthe transparent area 10 y of the laminated glass.

<Transparent Warp>

First, as shown in FIG. 3, the laminated glass 10 was placed withinclined angle in the same inclined angle as attaching the laminatedglass 10 to the vehicle, and the zebra pattern 60 was placed vehicleexterior-side. The zebra pattern 60 had a plurality of black lines 61provided on a white background. The black lines 61 were provided so asto form an angle of 45 degrees with respect to the lower side of thezebra pattern 60 and were parallel to each other.

The transparent warp was evaluated based on the state of warp of thezebra pattern 60 that generated near the boundary between thetransparent area 10 y and the light shielding area 10 x when the zebrapattern 60 was viewed from the vehicle interior-side of the laminatedglass 10.

FIGS. 4 and 5 are enlarged views of an example of the zebra pattern 60viewed from the vehicle interior-side of the laminated glass 10 in thevicinity of the boundary 51 between the transparent area 10 y and thelight shielding area 10 x surrounded by the dotted line in the laminatedglass 10 illustrated in FIG. 1. FIG. 4 is an example that shows notransparent warp, and FIG. 5 is an example that shows transparent warp.In FIG. 5, the black line 61 of the zebra pattern 60 appears to becurved and distorted near the boundary 51 between the transparent area10 y and the light shielding area 10 x. For this reason, the distancebetween the position where the extension line L, which is the left sideof the black line 61, intersects with the boundary 51 and the positionwhere the black line 61 actually intersected with the boundary 51 wasevaluated as warp (W) in accordance with the following criteria.

A: The warp (W) is less than 3 mm.C: The warp (W) is 3 mm or more.

<Heat Insulation>

The solar radiation reflectance Re of the laminated glass measured abovewas used for evaluation as an index of heat shielding property. All ofthe solar reflectance Re was all 20% or more, which was favorable.

(Film Being Pulled Inward>

In the front view, a state of the outer periphery of the infraredreflective film being pulled inward from the position in the laminatebefore the pressure bonding was visually observed. The evaluation wasperformed according to the following criteria.

A: The infrared reflective film was not pulled inward.B: A portion in which the outer periphery of the infrared reflectivefilm was pulled inward over a length of 5 mm or more was recognized.

The value of the thermal contraction ratio (H) in the direction, inwhich the thermal contraction rate of the infrared reflective film beingmaximum divided by the average value of the thermal contraction rate inthe direction in which the thermal contraction rate of the firstadhesive layer and the second adhesive layer being maximum iscalculated. The results are shown in Table 1.

Film properties of Properties of Ratio Infrared reflective film adhesivelayer of Properties of laminated glass Thermal Thermal ther- Maxi-contraction rate contraction rate mal Reflec- mum Evaluation DirectionOrtho- Direction Ortho- con- tive radius of Film Ex- of maxi- gonalThick- of maxi- gonal trac- color curva- Or- Trans- being am- mum con-direc- ness mum con- direc- tion Rv Re (at 10° ) ture ange Wrink- parentFoam- pulled ples traction tion [μm] traction tion rate (H) [%] [%] a*b* [mn] peel les warp ing inward 1 1.5% 1.5% 108 6.0% 5.0% 0.25 8.0 22.01.4 −8.5 860 A A A A A 2 2.0% 2.0% 108 6.0% 5.0% 0.33 8.0 21.9 1.4 −8.5860 A A A A A 3 1.5% 1.5% 100 6.0% 5.0% 0.25 11.1 22.3 1.5 −7.9 860 B AA A A 4 1.5% 1.5% 100 6.0% 5.0% 0.25 8.3 23.0 4.0  3.4 860 B A A A A 51.5% 1.5% 108 6.0% 5.0% 0.25 8.1 22.1 1.4 −8.6 1050 B A A A A 6 1.5%1.5% 108 8.5% 7.0% 0.18 8.0 22.0 1.4 −8.5 860 B B A A A 7 2.0% 2.0% 1083.0% 2.0% 0.67 8.1 22.0 1.4 −8.5 860 A A A A B 8 1.2% 1.2% 108 6.0% 5.0%0.2 8.1 22.7 1.4 −8.6 860 C C A A A 9 2.4% 2.4% 108 6.0% 5.0% 0.4 7.923.1 1.5 −8.6 860 A A C A A 10 1.5% 1.5% 75 6.0% 5.0% 0.25 8.0 21.6 1.4−8.5 860 C A A A A 11 1.5% 1.5% 130 6.0% 5.0% 0.25 8.0 21.9 1.5 −8.5 860A A A C A

DESCRIPTION OF THE REFERENCE NUMERALS

-   10: Laminated glass (windshield)-   1: First glass plate-   2: Second glass plate-   3: First adhesive layer-   4: Second adhesive layer-   5: Infrared reflective film-   6: Black ceramic layer-   10 x: Light shielding area-   10 y: Transparent area

1. A vehicle windshield comprising: a laminated glass in which a firstglass plate, a first adhesive layer, an infrared reflective film, asecond adhesive layer, and a second glass plate are laminated in thisorder, wherein a total thickness of the first glass plate and the secondglass plate is 4.1 mm or less, the infrared reflective film contains alaminate in which 100 or more resin layers having different refractiveindexes are laminated, the infrared reflective film has thermalcontraction rates, wherein a thermal contraction rate in the directionwhich the thermal contraction rate being maximum is 1.5% or more and2.0% or less, and a thermal contraction rate in the direction orthogonalto the aforementioned direction is 1.5% or more and 2.0% or less, andthe thermal contraction rates of the infrared reflective film in thepredetermined directions being reduction rates of lengths in thepredetermined directions before versus after maintaining the infraredreflective film at 150° C. for 30 minutes, and a thickness of theinfrared reflective film is 80 μm or more and 120 μm or less.
 2. Thevehicle windshield according to claim 1, wherein a visible lightreflectance of the laminated glass measured from a vehicle exterior-sideis 7% or more and 10% or less.
 3. The vehicle windshield according toclaim 1, wherein a color tone of the reflected light obtained byirradiating the laminated glass with light from a D65 light source fromthe vehicle exterior-side within an incident angle range of 10 to 60° inCIE1976L*a*b* chromaticity coordinates is −5<a*<3 and −12<b*<2.
 4. Thevehicle windshield according to claim 1, wherein a radius of curvatureof the laminated glass is 900 mm or less in the test area A specified byJIS R3212 (1998) of the vehicle windshield.
 5. The vehicle windshieldaccording to claim 1, wherein the infrared reflective film is formed byalternately laminating two kinds of resin layers having differentrefractive indexes, and a resin forming the resin layers contains atleast one kind selected from polyethylene terephthalate and polyethyleneterephthalate copolymer.
 6. The vehicle windshield according to claim 1,wherein the first adhesive layer and the second adhesive layer havethermal contraction rates, wherein a thermal contraction rate in thedirection which the thermal contraction rate being maximum is 2% or moreand 8% or less, and a thermal contraction rate in the directionorthogonal to the aforementioned direction is 2% or more and 8% or less,and the thermal contraction rates of the first adhesive layer and thesecond adhesive layer in the predetermined directions being reductionrates of lengths in the predetermined directions before versus aftermaintaining the infrared reflective film at 50° C. for 10 minutes, and adirection in which the thermal contraction rate of the infraredreflective film being maximum is orthogonal to a direction in which thethermal contraction rate of the first adhesive layer and the secondadhesive layer being maximum.
 7. The vehicle windshield according toclaim 1, wherein the first adhesive layer and the second adhesive layercontain polyvinyl butyral.
 8. The vehicle windshield according to claim1, wherein the thermal contraction rate in the direction which thethermal contraction rate of the infrared reflective film being maximumdivided by an average value of thermal contraction rate in the directionwhich the thermal contraction rates of the first adhesive layer and thesecond adhesive layer being maximum is a value of 0.2 or more and 0.6 orless.
 9. The vehicle windshield according to claim 1, wherein a blackceramic layer is provided on a main surface of the first glass plateand/or the second glass plate.
 10. The vehicle windshield according toclaim 9, wherein the black ceramic layer and the infrared reflectivefilm have a portion overlapping in a plan view.